1. Field of the Invention
The present invention relates to a scroll fluid machine usable in an air compressor, a vacuum pump, an expansion machine, and the like.
2. Description of the Related Art
In the related art, a scroll fluid machine includes a scroll fluid machine main body provided with: a cylindrical casing; a fixed scroll mounted on one end of the casing; an orbiting scroll provided in the casing to form plural compression chambers between the fixed scroll and the orbiting scroll; a driving shaft with a crank formed at one end thereof connected to the orbiting scroll in the casing and with the other end thereof protruding outward from the other end of the casing; and a cooling fan provided on the other end of the driving shaft outside the casing. Furthermore, the related art scroll fluid machine includes a cylindrical cooling duct totally surrounding the scroll fluid machine main body (see Japanese Published Unexamined Utility Model Application No. H5-78988).
One side of the cooling duct surrounds the outer peripheral side of the fixed scroll and the outer peripheral side of the casing through an annular space. The cooling duct is reduced in diameter at the periphery of the other end of the casing so as to conform the outer shape of the other end of the casing, and thereafter, increased again in diameter at the outer peripheral side of the cooling fan to surround the cooling fan through the annular space. Also, on one end of the cooling duct, an inlet is formed in a portion of the cooling duct opposed to the center of the fixed scroll. On the other end of the cooling duct, an upwardly opening outlet is formed in a portion of the cooling duct on the outer peripheral side of the cooling fan.
In the related art scroll fluid machine having such a structure, when the driving shaft is rotated by an electric motor, the orbiting scroll is allowed to perform an orbiting motion with respect to the fixed scroll, and the cooling fan is rotated, so that cooling air is sucked into the cooling duct through the inlet of the cooling duct. And then, the cooling air flows through the outer peripheral space of the fixed scroll and the casing formed within the cooling duct, and is compressed by a portion reduced in diameter of the cooling duct at the periphery of the other end of the casing to be sent to the inner periphery of the cooling fan. Finally, the cooling air sent to the inner periphery of the cooling fan is discharged from the outlet formed on the outer peripheral side of the cooling fan.
In the above-described scroll fluid machine according to the related art, since the scroll fluid machine main body is totally surrounded by the cooling duct, there has been a problem that the scroll fluid machine is increased in size.